This invention relates to adhesive articles and methods of applying and activating the adhesive articles to adhere to substrates using a fluid application aid. Preferably, the substrates are traffic devices such as traffic cones and the adhesive articles are retroreflective cone collars or sleeves.
Traffic devices are used to channel traffic, divide opposing traffic lanes, divide traffic lanes when two or more lanes are kept open in the same direction, and delineate the boundaries of temporary maintenance and utility work zones. The term xe2x80x9ctraffic devicexe2x80x9d includes, but is not limited to, bodies such as cones that are integrally formed from a flexible material that can be struck by a moving vehicle without significantly damaging the vehicle on impact, and having a base portion for supporting an upright member, preferably a conical or cylindrical member. Examples of traffic devices include cones, drums, tubes, stakes, and posts.
A common method of enhancing the visibility of such a traffic device, such as a traffic cone, is to adhesively apply reflectorized sheeting material to the exterior of the upright member in order to enhance the visibility of the traffic cone at night or other times of poor visibility. Typically, traffic cones for use on freeways include one or more reflective bands, which typically are formed from reflective sheeting, preferably retroreflective sheeting, adhered to the cone.
Such reflective sheeting may be applied manually, but such a process is slow and therefore expensive and requires considerable skill if speed and accuracy are desired. One such approach is to place a non-adhesive coated collar of retroreflective material over the cone after an adhesive has been applied to the cone, generally by brushing on a liquid adhesive. This is a messy procedure, labor intensive, does not assure 100% coverage of adhesive between the cone collar and the cone, and leaves adhesive residue that needs to be cleaned off the cone and cone collar. Stacking cones before the adhesive is dried is not recommended. A second approach is to apply a flat cone sleeve, which has adhesive coated on it, to the cone. This requires mechanical application equipment or great skill and care to get the retroreflective sheeting correctly placed on the cone without wrinkles.
What is needed is a method of applying adhesive articles, such as cone collars, quickly and easily to substrates, such as traffic cones. Although pressure sensitive adhesives (PSAs) would provide quicker and easier application, PSA articles are often difficult to apply to a substrate in a precise location and without air entrapment, primarily due to preadhesion or xe2x80x9cquick stickxe2x80x9d behavior of the PSA. This is particularly true for xe2x80x9caggressivexe2x80x9d PSAs that have high bond strengths and/or low temperature tack properties. Several methods and configurations have been developed to make application of PSA films and tapes easier.
For example, application aids such as detergent and water have been used to eliminate preadhesion. Formulations vary, but typically include water, a surfactant or lubricant, and a solvent (generally, an alcohol), the latter of which may speed bond formation and drying. The liquids tend to form a film between the adhesive and substrate, thus preventing contact and preadhesion. Unfortunately, most fluid application aids adversely affect the adhesive properties and prevent rapid formation of a strong bond between adhesive and substrate.
Dry application aids, such as particles, powders, or talcs are also useful in preventing preadhesion. While these techniques make application very easy and provide for easy positioning and repositioning, formation of a strong adhesive bond to the substrate is slow.
Certain conventional products use a random distribution of hollow glass microspheres partially embedded in the adhesive or nonadhesive spaced-apart posts as a means to prevent contact and preadhesion. Alternatively, a similar configuration is known in which the tops of the hollow microspheres protruding from the adhesive surface are coated by a thin layer of PSA. Pressure application crushes the microspheres permitting the adhesive to contact the substrate and form a strong bond instantly.
Microsphere and patterned adhesives have also been reported that exhibit repositionable properties. Deformable microspheres impart a rough or pebble-like surface and repositionable bond. In these cases, the adhesive films readily form weak, repositionable bonds to a substrate, but do not form a strong, permanent bond.
Topologically structured adhesives have also been described. For example, relatively large scale embossing of an adhesive has been described to permanently reduce the PSA/substrate contact area and hence the bonding strength of the PSA. Various adhesive layer topologies include concave and convex v-grooves or hemispheres, and other three dimensional shapes.
Although each of these methods could provide advantageous application of adhesive articles to substrates, other adhesive articles and methods are needed for application of adhesive articles, such as cone collars, to substrates, such as traffic cones.
This invention relates to adhesive articles and methods of applying and activating the adhesive articles to adhere to substrates. The adhesive article includes a surface on which is disposed an adhesive with a plurality of protrusions. The protrusions can be in the form of particles disposed on the adhesive surface (e.g., on a layer of adhesive). Alternatively, the adhesive can have a topologically structured adhesive surface such that the protrusions are a part of the adhesive layer. In yet another embodiment, the protrusions (referred to as xe2x80x9cstructured featuresxe2x80x9d in this embodiment) can be provided by fibers, particularly a fibrous woven or nonwoven web disposed on the adhesive surface. The methods involve applying the adhesive article to a substrate, positioning it, and allowing it to adhere to the substrate using a fluid (e.g., water, organic solvent, or a plasticizer) as an application aid. The application aid is a fluid at the temperature of application and/or activation of the adhesive article. That is, the application aid can be applied as a solid, and the temperature increased to melt the solid and form a fluid application aid. Although the fluid application aid is typically a liquid at the temperature of activation of the adhesive article, it is envisioned that it could also be a gas.
As used herein, a fluid application aid is applied to assist in activating the adhesive article to adhere to a substrate, and optionally, to assist in applying the adhesive article to the substrate. The fluid application aid could activate or temporarily deactivate the adhesive properties of the adhesive. It could also, or alternatively, activate or temporarily deactivate the adhesive properties of the protrusions (if they have such properties). The fluid application aid may temporarily decrease the adhesion and then allow the adhesion to build. The fluid application aid may be applied before or after the adhesive article and substrate come in contact with each other. Although such activation can occur by a variety of mechanisms, as long as there is an increase in the adhesion between the adhesive article and the substrate upon applying an application aid to the interface between the substrate and adhesive article, the method is within the scope of the present invention.
Preferably, an adhesive article according to the present invention is a retroreflective cone collar (i.e., sleeve) having an adhesive that facilitates correct positioning of the collar or sleeve on traffic cones, such as plasticized polyvinyl chloride (PVC), and further develops good adhesion to the cones over time. Although the present invention is preferably directed to traffic devices such as traffic cones and adhesive retroreflective cone collars (i.e., sleeves), the invention is not limited to such articles and substrates.
In one embodiment, the present invention provides a method of adhering an adhesive article to a substrate. The method includes: providing an adhesive article comprising a surface on which is disposed an adhesive with a plurality of protrusions; applying the adhesive article to a substrate (preferably, a flexible polymeric substrate) to form an interface between the adhesive and the substrate; and providing a fluid application aid to the interface between the adhesive and the substrate to promote adhesion between the adhesive article and the substrate. Preferably, the protrusions are in the form of particles disposed on the adhesive surface. A preferred group of particles include silica, talc, starch, glass, alumina, calcium carbonate, zeolites, nontacky adhesive precursor particles, and combinations thereof. Alternatively, the adhesive has a topologically structured surface with structured features.
In another embodiment, the invention provides a method of adhering an adhesive article to a substrate. The method includes: providing an adhesive article that includes a surface on which is disposed an adhesive (preferably, a plasticizer-activatable adhesive) with a plurality of protrusions provided by particles, fibers, a fibrous web, or combinations thereof; applying the adhesive to article to a substrate to form an interface between the adhesive and the substrate; and providing a fluid application aid to the interface between the adhesive and the substrate to promote adhesion between the adhesive article and the substrate. Preferably, the fluid application aid includes water and a surfactant. If desired, providing a fluid application aid to the interface between the adhesive and the substrate occurs simultaneously with applying the adhesive article to the substrate to form the interface. The fluid application aid can be provided to the adhesive article, the substrate, or both prior to applying the adhesive article to the substrate. Alternatively, the fluid application aid can migrate out of the substrate to which the adhesive article is applied (but typically not the backing that forms a part of the adhesive article).
Another embodiment of the invention is a method of adhering an adhesive article to a substrate that includes: providing an adhesive article that includes a surface on which is disposed a plasticizer-activatable adhesive with a plurality of plasticizer-activatable adhesive protrusions; applying the adhesive article to a substrate to form an interface between the adhesive and the substrate; and providing a fluid application aid to the interface between the adhesive and the substrate to promote adhesion between the adhesive article and the substrate.
The present invention also provides articles. In one embodiment, there is provided a retroreflective article that includes a retroreflective surface forming an exposed outer viewing surface, and an opposing surface (i.e., an outer surface of the article) on which is disposed a fluid-activatable adhesive with a plurality of fluid-activatable adhesive protrusions. Preferably, the fluid-activatable adhesive and fluid-activatable protrusions are plasticizer-activatable. Preferably, they are both prepared from the same or different plasticizer-activatable pressure sensitive adhesives.
Another embodiment is a retroreflective article that includes a retroreflective surface forming an exposed outer viewing surface, and an opposing surface on which is disposed an adhesive with a plurality of fluid-activatable protrusions. These protrusions are preferably plasticizer activatable, and more preferably prepared from plasticizer activatable adhesives.
Yet another embodiment is a retroreflective article that includes a retroreflective surface forming an exposed outer viewing surface, and an opposing surface on which is disposed a layer of an adhesive with a plurality of nontacky particles disposed thereon, wherein the nontacky particles are selected from the group of silica, talc, starch, glass, alumina, calcium carbonate, zeolites, nontacky adhesive precursor particles, and combinations thereof.
Another embodiment is a retroreflective article that includes a retroreflective surface forming an exposed outer viewing surface, and an opposing surface on which is disposed an adhesive with a plurality of fluid-activatable protrusions comprising fibers or a fibrous web.
Also are provided traffic devices, such as traffic cones, that include these retroreflective articles, which are preferably in the form of sheeting.
As a result of the present invention, cycle time to make, reflectorize, stack, package, and ship traffic devices such as cones, as well as labor, time, and costs are significantly reduced.
In this application:
xe2x80x9cadhesivexe2x80x9d refers to the adhesive composition, and may also refer to the adhesive layer of an adhesive article; it includes compositions that may or may not have adhesive properties at room temperature or temperature at which an article is applied to a substrate, but have adhesive properties upon activation (hence, an adhesive precursor is included within the term adhesive);
xe2x80x9cparticlexe2x80x9d refers to particulate material that may be spherical, cubic, irregularly shaped, solid, porous, hollow, elastic, inelastic, adhesive, nonadhesive, tacky, or nontacky;
xe2x80x9cpositionablexe2x80x9d means an adhesive surface can be placed against a substrate surface and easily slid over the surface into proper position without significantly preadhering to the substrate;
xe2x80x9csubstantially uniformly distributedxe2x80x9d means the unit average density of protrusions on the functional portion of the adhesive surface is uniform over the adhesive surface in a regular or random pattern as is necessary to make that adhesive surface positionable;
xe2x80x9csubstratexe2x80x9d means the surface upon which an adhesive article is applied; and
xe2x80x9ctackxe2x80x9d or xe2x80x9ctackyxe2x80x9d means instant contact adhesion between the adhesive and the substrate, which may be substrate specific (xe2x80x9cno tackxe2x80x9d or xe2x80x9cnontackyxe2x80x9d means that there is no such instant contact adhesion between the adhesive and the substrate).